Industry generally concerned with the production of cylindrically shaped containers typically has categorized them in terms of ranges of capacity. For example, those containers having volumetric capacities of from about eight gallons to fifty gallons are referred to as "drums", while intermediate size containers having volumetric capacities between about three and seven gallons are referred to as "pails" and containers below the latter size, carrying contents weighing from about four ounces to two pounds, generally are referred to as "tubs".
The design of the containers themselves are somewhat similar throughout the industry, however, lid structures which are applied to the containers are seen to vary somewhat. Typically, drums are fashioned of a fiber or cardboard material in view of the weight of the substances they are called upon to carry. However, metals and plastics also are used in drum fabrication. Generally, these materials will range from about 50 to 500 pounds per drum. As a consequence, the drums, when filled, typically will be warehoused and moved by personnel employing hand carts or forklifts and the like and thus, from time to time, will be tipped over or dropped. Because of the usually encountered chemical nature of the contents of the drums, lid securement for them is important to avoid spillage. Generally, to enhance strength and lid attachment, the rims of the drums are reinforced with annular metal chimes formed having a rim bead and an inwardly extending region or groove just below the bead, the mounting of which effects a deforming securement to the drum wall and which is employed to aid in locking lids to the drums. The lids typically closing the drums are formed as stamped metal components which are secured over the rim-chime assemblies with metal locking rings to assure the lid-tight security of the drums under tipping or drop conditions. As a consequence, to open up a drum, the locking ring is released and removed, whereupon the lid itself is removed and the drum contents then are accessed. To subsequently close the drum after removing some of the contents, the lid is repositioned and the locking ring is remounted, then tightened for securement. This open-close process becomes tedious where the contents of the drum are regularly accessed. For instance, drums containing swimming pool chemicals are opened and closed on a somewhat regular basis. As a consequence of the effort required for this process, the drum lids typically are merely positioned loosely on the drum rims and the locking ring feature of closure is ignored. This failure to secure the kids with the locking rings leaves the drums in an unsealed condition and leads to degradation of the remaining drum contained contents, i.e. the outgassing of chlorine from swimming pool chemicals. In the latter regard, chlorine is exothermic and inadvertent wetting of such chemicals can generate hazards.
Pails typically are formed of plastic (for example, polyolefins) with container bodies of a frusto-conical shape. The lids used to close them generally are discoidal in their general shape and typically are similarly fashioned of a resilient plastic. Usually, these lids are secured in position by structures which require the use of a screwdriver or similar prying instrument to open them. Unfortunately, subsequent access to the pails requires a similar prying implementation to frustrate the user from properly sealing the pails after using only a portion of their contents.
To retain lids upon pails, a configuration generally is provided for the pails which includes an integrally molded rim structure formed without resort to the chime structure of drums. This rim structure includes an upwardly disposed rim bead, as well as an engaging region formed inwardly and below the bead. Lid designs then vary but are concerned with a sealing structure using the rim bead and, often, the engineering region.
The smaller tub structures are generally configured of a vacuum formed, thermoformed, or injection molded material and the lid considerations for them look to the provision of a "tamper evident" feature. In the latter regard, it is desirable for many products to provide an indication as to whether any unauthorized opening of the lids of the tub has occurred subsequent to their being filled, for example with edible products. For the most part, the tamper evident procedures have been designed for that feature alone and not with considerations of improving the seal security of the lid-container combination in the first instance.
Stacking considerations are finding importance in both container and lid designs. Two aspects for such stacking occur, one stemming from requirements for transporting the containers empty, inasmuch as they maybe transported separately and the second consideration concerns the warehousing of the filled containers with lids attached. Where lids are tranported, it is desirable that they be stackable in some form of nesting relationship to facilitate their movement in the factory environment both where they are produced and at such time as they are employed to close a filled container. Particularly in the case of drums, the heavy weights involved become considerations in terms of warehousing and the like. Where pails and tubs are concerned, stacking requirements for both warehousing and retail display are assuming higher levels of importance. In some applications, it is preferred to pre-attach lids to containers for the purpose of a stacked shipment of the entire assembly. It then becomes desirable to provide a dual or first and second level clause arrangement. For such application the secondary latch is receiced following filling of the container.